Exactly. We don't ever need any new drugs. All the good drugs have already been invented.
If Americans are allowed to buy prescription drugs from foreign pharmacies, the prices that foreign pharmacies charge will go up, while American pharmacies will charge less. Simple supply and demand.
The cost of prescription drugs would thus level out across borders through unrestricted capitalism. Pharmaceuticals will still make their profit and if they choose to direct those profits into research, then that is their choice.
Drug research will continue as long as it is profitable.
Why should Americans be the only ones paying for the research?